1. Technical Field
The present invention relates to an inertial sensor.
2. Description of the Related Art
Recently, an inertial sensor has been used in various fields, for example, the military, such as an artificial satellite, a missile, an unmanned aircraft, or the like, vehicles, such as an air bag, electronic stability control (ESC), a black box for a vehicle, or the like, hand shaking prevention of a camcorder, motion sensing of a mobile phone or a game machine, navigation, or the like.
The inertial sensor generally adopts a configuration in which a mass body is bonded to a flexible substrate such as a membrane, or the like, so as to measure acceleration and angular velocity. Through the configuration, the inertial sensor may calculate the acceleration by measuring inertial force applied to the mass body and may calculate the angular velocity by measuring Coriolis force applied to the mass body.
A process of measuring the acceleration and the angular velocity by using the inertial sensor will be described in detail below. First, the acceleration may be obtained by Newton's law of motion “F=ma”, where “F” represents inertial force applied to the mass body, “m” represents a mass of the mass body, and “a” is acceleration to be measured. Among others, the acceleration a may be obtained by sensing the inertial force F applied to the mass body and dividing the sensed inertial force F by the mass m of the mass body that is a predetermined value. Further, the angular velocity may be obtained by Coriolis force “F=2 mΩ·v”, where “F” represents the Coriolis force applied to the mass body, “m” represents the mass of the mass body, “Ω” represents the angular velocity to be measured, and “v” represents the motion velocity of the mass body. Among others, since the motion velocity v of the mass body and the mass m of the mass body are values that are known in advance, the angular velocity Ω may be obtained by sensing the Coriolis force (F) applied to the mass body.
FIG. 1 is a cross-sectional view of an inertial sensor according to the prior art. Problems of the prior art will be described with reference to FIG. 1.
As shown in FIG. 1, an inertial sensor 10 according to the prior art is configured to include a mass body 2 that is provided under a central portion of a membrane 1 to generate displacement, a post 3 that are provided under an edge of the membrane 1 to support the membrane 1, and a bottom cap 4 that protects a bottom portion of the inertial sensor 10, or the like. Further, in order to control the inertial sensor 10 and calculate the acceleration and the angular velocity, the bottom portion of the bottom cap 4 is provided with an integrated circuit (IC) 5. In addition, the bottom portion of the integrated circuit 5 is further provided with a lead frame 6 so as to connect the integrated circuit 5 to external circuit boards (printed circuit board, or the like). As a result, the bottom portion of the inertial sensor 10 is provided with components having a predetermined thickness such as the integrated circuit 5, the lead frame 6, or the like, which increases the overall thickness of the inertial sensor 10, such that it is not possible to make the inertial sensor 10 thin.
In addition, pads 7 formed on the membrane 1 and the integrated circuit 5 are connected to each other through wire bonding 8, such that an area of the integrated circuit 5 needs to be wider than that of the bottom cap 4 so as to secure a space in which wire bonding 8 may be performed. Further, the integrated circuit 5 and the lead frame 6 are also connected to each other through the wire bonding 8, such that an area of the lead frame 6 needs to be wider than that of the integrated circuit 5 so as to secure the space in which wire bonding 8 may be performed. As a result, the area of the integrated circuit 5 and the lead frame 6 is sequentially increased as compared with the area of the bottom cap 4 which increases the overall area of the inertial sensor 10, such that it is not possible to make the inertial sensor 10 small.